Wireless communication is the transfer of information over a distance without the use of electrical conductors or wires. This transfer is actually the communication of electro-magnetic (EM) waves between a transmitting entity and remote receiving entity. The communication distance can be anywhere from a few inches to thousands of miles.
Wireless communication is made possible by antennas that radiate and receive the EM waves to and from the air, respectively. The function of the antenna is to “match” the impedance of the propagating medium, which is usually air or free space, to the source that supplies the signals sent or interprets the signals received.
Unfortunately, wireless handsets (cellular telephones) often generate interference with hearing aids, which leads to uncomfortable audible noise to the user or those around the user of the hearing aid. The Federal Communication Commission (FCC) will soon require that at least some of the wireless handsets offered by each wireless service provider meet certain standards aimed at reducing interference with hearing aids. These Hearing Aid Compatibility (HAC) standards stipulate that the electric and magnetic field strength within at least six squares of a nine square measurement grid centered on the speaker of a qualifying handset and spaced from the handset by 1 centimeter, be below predetermined limits. FIG. 1 depicts a “candy bar” form factor wireless handset 100 with the aforementioned nine square measurement grid 102.
It has been found that it is particularly difficult to make “candy bar” wireless handsets that meet the FCC HAC requirements. Most currently available “candy bar” wireless handsets use internal antennas that are located either at the bottom or top end of the handset's internal printed circuit board. Examples of internal antennas include the Planar Inverted “F” Antenna (PIFA) and the more advanced Folded Inverted Conformal Antenna (FICA). Generally, internal antennas of wireless handsets use the ground plane of the wireless handset's internal circuit board and/or other conductive parts of the handset as a counterpoise in at least some operating bands (e.g., operating bands in the 800 MHz to 900 MHz range). Consequently, high electric field regions occur both near the antenna and at the opposite end of the handset (at the remote end of the counterpoise.) Such high electric fields are problematic for meeting the FCC HAC requirements. A few methods for mitigating the electric fields have been proposed, but all of them require additional parts to be added and/or extra complexity.
Therefore, a need exists to overcome the problems with the prior art as discussed above.